3-Stream S-wheel and cooling mode operation

ABSTRACT

An improved adiabatic saturation cooling machine of the opencycle type and method of operation in which the capacity of the machine is increased by routing by-pass streams of air through either the S-wheel alone or both the S- and the L-wheel. The amount of these by-pass streams are from 0 to 100 percent that of the main exhaust stream of air passing from the room through the S-wheel. In the first embodiment the by-pass air is outside air and is directed to the regenerative &#39;&#39;&#39;&#39;side&#39;&#39;&#39;&#39; of the S-wheel. Such a by-pass stream ranging from 95*F to 80*F will cool the air from the S-wheel an additional 2.6* to 5.9*F below that capable by the room air exhaust stream alone. The outside air by-pass stream may be passed directly through the S-wheel or pretreated by passing through an E-pad. In the second embodiment, where there is sufficient air supplied to the burner section to regenerate the L-wheel, a portion of the primary room exhaust air stream is recirculated as a by-pass stream to the input face of the L-wheel. A third embodiment is directed to incoming air bypassing the E-pads from the cooling side of the S-wheel. A fourth embodiment is directed to a return by-pass for directing the first stream of incoming L-wheel air back out the regenerative &#39;&#39;&#39;&#39;side&#39;&#39;&#39;&#39; of the L-wheel.

United States Patent Weil [ Apr. 29, 1975 3-STREAM S-WHEEL AND COOLINGMODE OPERATION [75] Inventor: Sanford A. Weil, Chicago. Ill.

[73] Assignee: Gas Developments Corporation,

Chicago. 111.

[22] Filed: Feb. 23, 1971 [211 App]. No.: 118,196

Related US. Application Data [63] Continuation of Scr. No. 791.000. Feb.23. 1971.

Primary E.\'uminerCharles Sukalo Attorney, Agent. or FirmMolinareAllegretti, Newitt & Witcoff TV /CAL OUTS/DE FRESH A/R DRYBl/LB- 95'EWETBULB- 80F [57] ABSTRACT An improved adiabatic saturation coolingmachine of the opencycle type and method of operation in which thecapacity of the machine is increased by routing bypass streams of airthrough either the S-wheel alone or both the S- and the L-wheel. Theamount of these bypass streams are from 0 to 100 percent that of themain exhaust stream of air passing from the room through the S-wheel. 1nthe first embodiment the bypass air is outside air and is directed tothe regenerative side of the S-wheel. Such a by-pass stream ranging from95F to 80F will cool the air from the S-wheel an additional 2.6 to 59Fbelow that capable by the room air exhaust stream alone. The outside airby-pass stream may be passed directly through the S- wheel or pretreatedby passing through an E-pad. 1n the second embodiment. where there issufficient air supplied to the burner section to regenerate the L-wheel, a portion of the primary room exhaust air stream is recirculatedas a by-pass stream to the input face of the L-wheel. A third embodimentis directed to incoming air bypassing the E-pads from the cooling sideof the S-wheel. A fourth embodiment is directed to a return by-pass fordirecting the first stream of incoming L-wheel air back out theregenerative side of the L-wheel.

18 Claims, 5 Drawing Figures BYPASS PRECOOL ING A/R i l i 30 I I /2 2 4-HEEL i ROTATION 2 I r ,5, 1 BURNER fi:::: GAS

ROTATION 4 S-h HEEL p Li if 33 l l E AP0/f7?AT/VE1 I :P 7 l3 l 1 I 6 itQ TYP/CAL ROOM A/R 0R) BULB 75'5 WET BULB 63 F 3-STREAM S-WHEEL ANDCOOLING- MODE OPERATION This application is a continuation ofapplication No. 791,000 filed Feb. 23, I971 and now abandoned.

This invention relates to air conditioning, and in particular toimprovedefficiency of cooling involving improved process and apparatusfor an open-cycle air conditioning unit.

Open-cycle air conditioners are well known in the art. One system. knownas the Munters environmental control system (MEC) unit, is described inUS. Pat. No. 2,926,502. Basically, open-cycle air conditioners operateby dehumidification and subsequent cooling of air wherein moist air isconditioned by a 3-stage process to produce cool relatively dry air.

Open-cycle air conditioning systems comprise essentially four sections,considered in order from the interior room in which the air is to beconditioned toward the exterior: 1) an adiabatic evaporating sectiondesignated an E-pad, 2) a S-wheel section, for transfer of sensible heatto and from air, 3) a heating section, and 4) a L-wheel section fortransfer of latent heat of condensation and evaporation. MEC units arefuel gas or electrically-operated environmental control systems whichprovide cooling in the summer, heating in the winter, year-aroundcontrol of humidity, and effective removal of dust and pollen. Theprinciple involved in the cooling effect of the system is that dry, warmair can be simultaneously cooled and humidified by contacting it withwater. In geographic areas where the air is both warm and humid, it mustbe dried before it can be cooled by evaporation. During the heatingseason of autumn, winter and spring, the unit can be used to warm andhumidify cold, dry air by making minor changes in the units operatingcycle.

However, the present Munters type of units suffer from an inadequatecooling step involved in the S- wheel section of the machine. Thepresent S-wheels used in this type of machine are approximately 90percent efficient. For example, air from the dehydrating L-wheel has anaverage temperature on the order of 190F and is cooled to 75.7F by theS-wheel during the cooling half of the cycle. In turn, the S-wheel isregenerated, i.e., recooled after taking up heat from the incoming air,by a 63F stream of air exhausting from the room during the regenerativehalf of the cycle. This rather high temperature of the conditioned airfrom the S-wheel (75.7F) is limited primarily by the wheel efficiencyand, to some degree, to the outside ambient air temperature andhumidity.

It is therefore an object of this invention to provide an improvedopen-cycle air conditioner assembly in which the cooling efficiency ofthe S-wheel is increased.

It is another object of this invention to provide an improved process ofconditioning air whereby lower con ditioned air temperatures areachieved, and recirculation of room air is possible when so desired.

Another object of this invention is to provide improved process andapparatus for rejecting a first segment of moist air input through the L-wheel back out through the regenerative side of said wheel;

Another object of this invention is to provide improved process andapparatus for bypassing air from the outside through the 'S-wheel, orfirst through an E-pad and then the S-wheel, or from the exit side ofthe S-wheel to the input side of the Lwheel, or from the cooling side ofthe S-wheel to the room without passing through an E-pad, and thevarious combinations of bypasses thereof.

Additional objects of this invention will be evident from the detaileddescription which follows.

The objects of this invention are achieved by directing streams of airthrough either the regenerative side of the S-wheel, and/or the inputface of the L-wheel. In the first embodiment, the S-wheel is precooledby directing a stream of outside air through the wheel prior to passingthe primary or main cooling stream of air exhausting from the roomthrough the wheel. In the apparatus .and method of this invention, asthe S-wheel passes through the regenerative portion of the cycle, afirst, precooling, stream of air is passed through the wheel. Thisprecooling, or secondary air, may be ambient outside air and can be anamount less, as large, or larger than, the amount of the room exhaustair. The secondary air amount can be varied to achieve the desired finalconditioned air temperature, and will be typically an amount of 20-100percent of the main stream passing through from I to 50 percent, andpreferably 5 to 30 percent, of the surface area of the S-wheel. Theparticular area value within this range may be determined to avoidexcessive blower power requirements. Thereafter the room exhaust airstream. called the main or primary stream, is passed through anappropriately proportioned fraction of the S-wheel. Usually the amountof primary air exhausted is equivalent to the amount entering the room,but may be more or less as inside an outside environmental factorspermit depending on the machine capacity.

In a second embodiment, which is preferably operated in conjunction witha bypass stream of outside air, a portion of the primary exhaust streamis directed as a bypass stream to the input face of the L-wheel.

Two other embodiments involve, respectively, passing incoming airdirectly to the room from the cooling side of the S-wheel withoutpassing through an E- pad, in order to achieve humidity control andrejecting a first segment of moist air input through the L-wheel fromthe outside back out through the regenerative side of the L-wheel.

In the Figures like numbers in different figures indicate similar orequivalent parts. The arrows show the air flow paths and are indicatedin dashed lines where the air passes through an E-pad, a wheel, or aduct not shown in cross-section. All ducts are shown in diagrammaticcross-section except the portion between the re generative side E-padand S-wheel and a portion of the recycle duct, which are shown in planview, and the duct of FIG. 5 which is shown in perspective.

FIG. 1 shows diagrammatically one embodiment of an open-cycle airconditioning system of this invention wherein the Swheel is precooled bya stream of secondary, bypass air;

FIG. 2 shows digrammatically another embodiment of an opencycle airconditioning system of this invention employing a pretreated stream ofprecooled bypass air;

FIG. 3 is an exploded perspective view of the interior face of anS-wheel showing qualitatively the portions of the wheel exposed to theprecooling bypass stream and the primary cooling air streamsrespectively;

FIG. 4 shows diagrammatically another embodiment employing ducting forrecirculation of room air; and

FIG. 5 shows a perspective view partly in section of a return conduitfor passing input air back out the L- wheel regenerative side.

Referring now to FIG. 1, a conventional open-cycle system operating inthe cooling mode may be described as follows: The incoming outdoor airis shown by the downwardly pointing arrow on the left side of thediagrammatic representation of an open-cycle unit 1. To start thecooling half of the cycle, the warm, moist outside air is drawn into theunit by means of a fan 2 and passed through the input side 30 of a hot,dry L-wheel 3 which serves the function of taking up (sorbing) moisturefrom the air. In the figures the L-wheels rotate clockwise, from left toright as seen from the top. A major portion of the latent heat ofcondensation liberated by the water in being absorbed in the L-wheel istaken up by the air as it passes through the wheel.

The air leaving the L-wheel is not uniform in temperature or humidity. Ihave found that air which first passes through the L-wheel after thewheel has left the regenerative half of the cycle should not continue onto the S-wheel but be diverted into the regenerative stream. 1 havediscovered that this portion of air serves primarily to cool the L-wheelwith very little dehydration of the air. I have determined that at usualair velocities (about 200 feet per minute through the L-wheel rotatingat a representative speed of 34 minutes per revolution), about a fifthof a minute for each 6 inches of wheel depth is required for thiscooling section. This may also be expressed as the equivalent angle ofrotation, 0, of between about l7-24 per 6 inches wheel depth. Theefficiency of the machine is enhanced if this portion of the air streamleaving the L-wheel is sent into the regenerative stream immediatelyupstream of the burner, as shown in FIG. 5. FIG. 5 shows that the firstportion of incoming air passing through a segment of the L-wheelidentified by the angle 6 is diverted in a bypass duct 40 back throughthe regenerative side of the L-wheel by means of baffle 41 as shown bythe arrow 42. As shown it can be diverted through the preceeding segmentof the L-wheel 3 in the regenerative half of the cycle, or alternativelythrough other segments of the L-wheel, for example, the first segment ofthe wheel rotating into the regenerative half of the cycle, as shown inphantom lines 43. Alternatively, the portion of the duct protruding intothe regenerative side may be eliminated with the rejected air segmentmingling with the exiting regenerative air stream. The remaining portionof the air stream leaving the L-wheel while still hot, is sufficientlydry for the purposes of the machine up to a period of 2 minutes for each6 inches of wheel depth in mild climate region such as Chicago. This drysegment is only 1.5 minutes in more severe humidity areas such as Texas.

The hot, dry incoming air, I, then passes through the cool portion 4 ofa rotating S-wheel wherein it gives up most of its sensible heat to thewheel. For best S-whee] operation, the S-wheel should rotate in adirection opposite to the L-wheel. The two wheels may rotate in the sameor opposite directions, and clockwise rotation of the L-wheel is not anabsolute requirement. Since the S-wheel is water impervious andrelatively cool, the air is cooled with no change in moisture content.In the ordinary cycle, at usual design conditions, the averagetemperture of the air incoming to the S-wheel at 5 after having passedthrough the L-wheel is on the order of about 190F. Typically, awell-designed S-wheel is capable of on the order of percent efficiency.With the S-wheel 90 percent efficiency, in the conventional systems, theincoming hot dry air from the L-wheel at 5 during the cooling half ofthe cycle is thus cooled to about 75.7F at 6 prior to passage throughthe evaporative pad 7 and then into the room 8.

Exiting from the S-wheel at 6, relatively cool, relatively dry airpasses over or through evaporative pads 7, where water is evaporated andthe air is humidified. Simultaneously, the latent heat of vaporizationis extracted from the air (in order to evaporate the water into theair), thereby cooling the air. The resulting air issuing into a room orspace to be conditioned 8 is typically at a lower dry bulb temperaturethan the outside air with about percent relative humidity. This cooled,moist air is thus conditioned for room comfort. If desired, apreselected humidity level can be achieved by passing a controlledportion of stream 6 around the E-pad 7, e.g. via bypass duct 33 (FIG.1).

The regenerative half of the cycle commences with typical room airpassing through evaporative pads 7' where the air is cooled whileevaporating water from the pad. The resultant cool, relatively moist airis then passed over the hot portion 4 of the S-wheel which is cooledthereby. It should be recalled that the Swheel has been heated by takingup sensible heat from the hot dry air produced from the L-wheel, thedehydrating wheel. The air incoming to the S-wheel after passing throughthe evaporative pads is ordinarily on the order of 63F.

Continuing with the regenerative half of the cycle, the moist airpassing through the right side of the S- wheel 4, while cooling therotating S-wheel so that it may repeat its portion of the cooling halfof the cycle at 4, is warmed. This warm, moist air then passes through aheating section 9. This heating section typically employs a gas burneror other heat source where the temperature is greatly increaseed,producing very hot air, of low relative humidity, typically on the orderof 325F. This very hot air, because of the heat, has a low relativehumidity which, when passed through the moist portion of the L-wheel 3dries the wheel. The very hot air is then exhausted to the outside 10completing the regenerative half of the cycle. Meanwhile, the heated,dried L-wheel rotates into position to function in the cooling half ofthe cycle where it again sorbs moisture from incoming outdoor air.

In one embodiment of this invention (still referring to FIG. 1), astream of bypass air 15 (secondary air) is drawn in by means of fan 11(or optionally by fan 11 shown in phantom lines) into the duct 12 shownat one side of the apparatus. The air shown by the dashed arrow BP isdirected by suitable ducting 13 through a portion of the S-wheel. Theportion of the S-wheel which receives the bypass air from the outside ison the order of from l50 percent. of the surface area of theregeneration side of the S-Wheel, preferably 5-30 percent; that segmentis identified as segment B in FIG. 3. As shown in the figures, thatportion is preferably a portion of the rightside of the S-wheel, but maybe partially or entirely on the left side.

The term side has the meaning here of portion, and the regenerative sideneed not be identical to half the S-wheel, as shown in FIG. 3 by thephantom line 14. For example, ducting to and from the. wheel faces maybe arranged to divide the wheel faces area into any desired number ofparts and proportons, including radial (angular) or concentric annularportions, or the like. Where the wheel faces area is divided into threesegments for l the input air being conditioned, 2) the secondaryprecooling air, and 3) the primary exhaust air, respectively, only theinput air portion would be termed the input side, with the remainingportions constituting the regenerative side" even though they mayconstitute, say, 2/3 of the wheel area.

Continuing with the regenerative portion of the method and apparatus ofthis invention, 100 percent of the room exhaust air (the main or primaryair stream indicated by dashed arrow M in the figures) is directedthrough the remaining portions of the regenerative side or portion ofthe S-wheel as shown in segment creased capacity of the machine. Wherean improved machine of this invention is to have the original capacity,the blower requirements can actually be lower than the original machine.

By way of example, the various potential gains through use of a bypassstream of this invention can be illustrated in the following table whichrelates the total water consumption, the blower power requirements, thedelivered temperature, and the amount of bypass air used as compared toconventional machines of same capacity. In this example the bypassstream is precooled as in FIG. 2, and the amount of the precooled bypassstream is expressed in terms of a ratio of its mass relative to that ofthe primary or room exhaust stream C of FIG. 3. For example, in thisembodiment, where 5 mass.

Table I Ratio Rclative Temperature Relative Relative Bypass ofConditioned Air Total Water Total Blower Air/Room Delivered to E-pad, FConsumption, Power, Exhaust Air (at 6 in FIG. 2) Ratio Ratio 0 l.() l.()[/9 -2.8 .92 .76 2/8 4.7 .90 .69 3/7 5.6 .95 .72 4/6 5.9 1.05 .77 l 5.91.16 .97

the room exhaust or primary air stream and the input air stream passingfrom 5 to 6 are volumetrically equal, and the secondary bypass airstream passing through segment B of the S-wheel (see FIG. 3) is on theorder of 95F, the l90F stream passing inwardly from 5 via face 31through segment A of the S-wheel (see FIG. 3) will be cooled to about73.1F at 6. In contrast, where no bypass air stream is used, only 75.7Fwould be achieved at 6. Thus, this embodiment of the invention resultedin about a 2.6F drop at 6, and a corresponding efficiency increase.

Referring now to FIG. 2, a second embodiment of the invention employs abypass air stream 15 routed first through an evaporative pad 32, viaducting 13 before passing through an appropriate portion of the S-wheel4. In passing first through the evaporative pad, a 95F bypass air streamis evaporatively cooled to about 80F at 16. The water vapor added may bepreselected in amount up to adiabatic saturation. This results in animprovement in the cooling of the conditioned stream 6 of 59F over thatacheived without the bypass, where the same main and input air stream asabove are used. This 5.9F improvement corresponds to an increase of 24percent in machine capacity if no other changes are made.

As can be seen from FIG. 3, the bypass air stream BP from the outsidepassing through the appropriate B of the S-wheel operates to precool theS-wheel since the wheel rotates first into the bypass segment B from thecooling half cycle portion or side 4. Thus, the S-wheel of thisinvention employs the use of three streams of air, the added one beingoutside air, either untreated or evaporatively precooled. The apparatusof this invention thus has an equivalent cooling efficiency of over 95percent, in cooling the hot air I incoming from the L-wheel at 5, ascompared to efficiency figures of on the order of 90 percent for MECunits not employing the bypass of this invention.

Although the use of a third stream increases the blower requirements,the increase is offset by the in- When the bypass airzprimary exhaustair ratio is greater than 2 3, the room exhaust air may be recirculatedas shown in the embodiment of FIG. 4. In this embodiment the burner airis supplied completely by the bypass air. Even where there is less than2 3 ratio, a portion of the room exhaust air can be recirculated. Undermild conditions, where full burner operation is not used, fullrecirculation is possible even though the ratio is less than 2 3.

Referring now to FIG. 4, this embodiment of this invention employs abypass stream routed by duct 13 as in the embodiment of FIG. 2 describedabove. The room exhaust stream, instead of going to the L-wheel on theregenerative side, is directed, via suitable ducts 20, 21, 22 to theinput side of the L-wheel. When not in use, louvre 23, pivotable at 24,is disposed in its closed position 25 and the flow-through louvres 26 induct 20 opened to provide operation as in the device of FIG. 2. Themachine of this embodiment is adjustable between zero and fullrecirculation, e.g. by adjustment of the louvres 23 and/or 26. Thusadvantage may be taken of greater efficiency on mild days without theuse of this recirculation method, while on severely hot and humid daysrecirculation permits greatest efficiency.

During the heating season, the MEC unit of this invention has thecapability of delivering heated, filtered and controlled humidificationof air to the space to be conditioned. Conversion of the unit fromcooling to heating is accomplished very simply by stopping rotation ofthe S-wheel and increasing the speed of rotation of the L-wheel. Duringthe heating cycle, exhaust air from the conditioned space is heated bythe gas burner and this heat is then transferred to the rotating L-wheelas exhaust air passes through the L-wheel to the outside. The heat thusstored in the L-wheel is utilized when relatively cold outside air isdrawn through the L-wheel, which in this mode of operation functions asa very efficient heat exchanger. Moisture generated by combustion of gasis recycled to the incoming air to provide humidity levels adequate inmost cases. Air

heated by the L-wheel then passes through the stationary S-wheel. Ifnecessary, the air may be passed through a water curtain or evaporativepad where dust or pollen is removed and the air is further humidified toa desired level before it is delivered to the conditioned space.Optionally, all the air may pass directly to the space via bypassconduit 33. In this mode of operation the bypass air system 11, 12, 13shown in FIGS. 1, 2 and 4 is not utilized.

Such open cycle environmental control systems in both the heating andcooling modes can utilize 100 percent outside air, unlike most airconditioning systems, which, except on mild days, must recycle insideair. Because of the water curtain or evaporative pads employed, all suchair is subject to removal of dust and pollen before it enters theconditioned space.

I claim:

1. In a method for cyclic conditioning of air including the steps of:

l. passing outside air as a first air stream through a first portion ofa rotating dehydrating L-wheel to produce relatively dry air;

2. passing said relatively dry air through a first portion of a rotatingsensible heat exchanging S-wheel to produce relatively cool dry air, foruse in an enclosed space;

3. withdrawing a primary stream of exhaust air from said conditionedspace through an evaporative pad;

4. passing said exhaust air as a second air stream through a secondportion of said S-wheel whereby.

said S-wheel is cooled;

5. passing a portion of said exhaust air through a heating section;

6. passing said exhaust air through a second portion of said L-wheel tobe exhausted to the outdoors;

said steps 1 and 2 comprising the cooling half of said conditioningcycle and said steps 46 comprise the regenerative half of saidconditioning cycle, the improvement which comprises in combination theadded step of:

7. directing a stream of bypass air as a third air stream through aportion of said S-wheel prior to being cooled by said primary exhaustair stream whereby heat is exchanged between said three streams, saidS-wheel is precooled, and its effciency increased without an increase inits mass.

2. A method as in claim 1 wherein said third stream of bypass air issupplied in an amount of from about to 100 percent of the primary roomexhaust air stream.

3. A method as in claim 1 which includes the added step of passing aportion of said primary exhaust stream exiting from said second portionof said S-wheel to said first portion of said L-wheel.

4. A method as in claim 1 which includes the added step of passing thehot air exiting from that portion of said L-wheel which is rotating fromsaid regenerative half of said cycle into said cooling half of saidcycle back through said second portion of said L-wheel.

5. A method as in claim 1 which includes the added step of passing aportion of said relatively cool dry air exiting from said first portionof said S-wheel through an evaporative pad.

6. A method as in claim 1 which includes the step of passing a portionof said third stream of bypass air through an evaporative pad prior tobeing directed through said S-wheel.

7. A method as in claim 6 wherein said third stream of bypass air issuppled in an amount of from about 20 to percent of the room exhaustair.

8. A method as in claim 6 which includes the added step of passing thehot air exiting from the portion of said L-wheel which is rotating fromsaid regenerative half of said cycle into said cooling half of saidcycle back through said second portion of said L-wheel.

9. A method as in claim 6 which includes the added step of passing aportion of said relatively cool dry air exiting from said first portionof said S-wheel through an evaporative pad.

10. A method as in claim 3 which includes the added step of passing aportion of said relatively cool dry air exiting from said first portionof said S-wheel through an evaporative pad.

11. A method as in claim 4 which includes the added step of passing aportion of said primary exhaust stream exiting from said second side ofsaid S-wheel to said first portion of said L-wheel.

12. A method as in claim 6 which includes the added step of passing aportion of said primary exhaust stream exiting from said second portionof said S-wheel to said first portion of said L-wheel.

13. In a method for cyclic conditioning of air including the steps of:

l. passing outside air as a first air stream through a first portion ofa rotating dehydrating L-wheel to produce relatively dry air;

2. passing said relatively dry air through a first portion of a rotatingsensible heat exchanging S-wheel to produce relatively cool dry air, foruse in an enclosed space;

3. withdrawing a primary stream of exhaust air from said space throughan evaporative pad;

4. passing said exhaust air as a second air stream through a secondportion of said S-wheel whereby said S-wheel is cooled;

5. passing a portion of said exhaust air through a heating section;

6. passing said exhaust air through a second portion of said L-wheel tobe exhausted to the outdoors;

said steps 1 and 2 comprising the cooling half of said conditioningcycle and said steps 46 comprising the regenerative half of saidconditioning cycle, the improvement which comprises in combination theadded step of:

7. passing a portion of said primary exhaust stream exiting from saidsecond portion of said S-wheel to said first portion of said L-wheel aspart of said first 7 air stream.

14. A method as in claim 13 which includes the added step of passing thehot air exiting from that portion of said L-wheel which is rotating fronsaid regenerative half of said cycle into said cooling half of saidcycle back through said second portion of said L- wheel.

15. A method as in claim 4 wherein said air from said first portion isthe amount passing through from l724 angular rotation of said L-wheelper 6 inches L-wheel depth.

16. A method as in claim 1 wherein said S- and L- wheels are rotated inopposite directions.

17. A method as in claim 13 wherein said 5- and L- wheels are rotated inopposite directions.

18. A method as in claim 4 wherein said 5- and L- wheels are rotated inopposite directions.

1. In a method for cyclic conditioning of air including the steps of: 1.passing outside air as a first air stream through a first portion of arotating dehydrating L-wheel to produce relatively dry air;
 2. passingsaid relatively dry air through a first portion of a rotating sensibleheat exchanging S-wheel to produce relatively cool dry air, for use inan enclosed spAce;
 3. withdrawing a primary stream of exhaust air fromsaid conditioned space through an evaporative pad;
 4. passing saidexhaust air as a second air stream through a second portion of saidS-wheel whereby said S-wheel is cooled;
 5. passing a portion of saidexhaust air through a heating section;
 6. passing said exhaust airthrough a second portion of said Lwheel to be exhausted to the outdoors;said steps 1 and 2 comprising the cooling half of said conditioningcycle and said steps 4-6 comprise the regenerative half of saidconditioning cycle, the improvement which comprises in combination theadded step of:
 7. directing a stream of bypass air as a third air streamthrough a portion of said S-wheel prior to being cooled by said primaryexhaust air stream whereby heat is exchanged between said three streams,said S-wheel is precooled, and its efficiency increased without anincrease in its mass.
 2. passing said relatively dry air through a firstportion of a rotating sensible heat exchanging S-wheel to producerelatively cool dry air, for use in an enclosed spAce;
 2. A method as inclaim 1 wherein said third stream of bypass air is supplied in an amountof from about 20 to 100 percent of the primary room exhaust air stream.2. passing said relatively dry air through a first portion of a rotatingsensible heat exchanging S-wheel to produce relatively cool dry air, foruse in an enclosed space;
 3. withdrawing a primary stream of exhaust airfrom said space through an evaporative pad;
 3. A method as in claim 1which includes the added step of passing a portion of said primaryexhaust stream exiting from said second portion of said S-wheel to saidfirst portion of said L-wheel.
 3. withdrawing a primary stream ofexhaust air from said conditioned space through an evaporative pad; 4.passing said exhaust air as a second air stream through a second portionof said S-wheel whereby said S-wheel is cooled;
 4. A method as in claim1 which includes the added step of passing the hot air exiting from thatportion of said L-wheel which is rotating from said regenerative half ofsaid cycle into said cooling half of said cycle back through said secondportion of said L-wheel.
 4. passing said exhaust air as a second airstream through a second portion of said S-wheel whereby said S-wheel iscooled;
 5. passing a portion of said exhaust air through a heatingsection;
 5. A method as in claim 1 which includes the added step ofpassing a portion of said relatively cool dry air exiting from saidfirst portion of said S-wheel through an evaporative pad.
 5. passing aportion of said exhaust air through a heating section;
 6. passing saidexhaust air through a second portion of said L-wheel to be exhausted tothe outdoors; said steps 1 and 2 comprising the cooling half of saidconditioning cycle and said steps 4-6 comprise the regenerative half ofsaid conditioning cycle, the improvement which comprises in combinationthe added step of:
 6. A method as in claim 1 which includes the step ofpassing a portion of said third stream of bypass air through anevaporative pad prior to being directed through said S-wheel.
 6. passingsaid exhaust air through a second portion of said L-wheel to bEexhausted to the outdoors; said steps 1 and 2 comprising the coolinghalf of said conditioning cycle and said steps 4-6 comprising theregenerative half of said conditioning cycle, the improvement whichcomprises in combination the added step of:
 7. passing a portion of saidprimary exhaust stream exiting from said second portion of said S-wheelto said first portion of said L-wheel as part of said first air stream.7. A method as in claim 6 wherein said third stream of bypass air issuppled in an amount of from about 20 to 100 percent of the room exhaustair.
 7. directing a stream of bypass air as a third air stream through aportion of said S-wheel prior to being cooled by said primary exhaustair stream whereby heat is exchanged between said three streams, saidS-wheel is precooled, and its efficiency increased without an increasein its mass.
 8. A method as in claim 6 which includes the added step ofpassing the hot air exiting from the portion of said L-wheel which isrotating from said regenerative half of said cycle into said coolinghalf of said cycle back through said second portion of said L-wheel. 9.A method as in claim 6 which includes the added step of passing aportion of said relatively cool dry air exiting from said first portionof said S-wheel through an evaporative pad.
 10. A method as in claim 3which includes the added step of passing a portion of said relativelycool dry air exiting from said first portion of said S-wheel through anevaporative pad.
 11. A method as in claim 4 which includes the addedstep of passing a portion of said primary exhaust stream exiting fromsaid second side of said S-wheel to said first portion of said L-wheel.12. A method as in claim 6 which includes the added step of passing aportion of said primary exhaust stream exiting from said second portionof said S-wheel to said first portion of said L-wheel.
 13. In a methodfor cyclic conditioning of air including the steps of:
 14. A method asin claim 13 which includes the added step of passing the hot air exitingfrom that portion of said L-wheel which is rotating fron saidregenerative half of said cycle into said cooling half of said cycleback through said second portion of said L-wheel.
 15. A method as inclaim 4 wherein said air from said first portion is the amount passingthrough from 17*-24* angular rotation of said L-wheel per 6 inchesL-wheel depth.
 16. A method as in claim 1 wherein said S- and L-wheelsare rotated in opposite directions.
 17. A method as in claim 13 whereinsaid S- and L-wheels are rotated in opposite directions.
 18. A method asin claim 4 wherein said S- and L-wheels are rotated in oppositedirections.